There has been substantial work directed towards development of implantable defibrillation systems that avoid the necessity of a thoracotomy. Systems that deliver a defibrillation pulse between one or more endocardial electrodes and an active defibrillator housing are disclosed in U.S. Pat. No. 4,727,877 issued to Kallok; U.S. Pat. No. 4,922,927 to Fine et al.; U.S. Pat. No. 5,133,353 to Hauser; and U.S. Pat. No. 5,261,400 to Bardy, all of which are incorporated herein by reference. As used herein, the words "housing", "enclosure", "case", and "can" are synonymous.
If a device is chosen to have an active can and is placed pectorally, it is unlikely that this decision would be changed in the future. If a lead is used subcutaneously and the inactive can implanted abdominally, it is again unlikely that there would be reason to change this, to "activate the can". Even if this decision were reversed, a surgical procedure would likely be required to reposition the can for effective use as an electrode. Therefore, external programmability of this choice of active or inactive can is not needed, allowing the device to be made simple to manufacture and simple to use.